Esters and compositions containing same



United States Patent Ofiice 3,223,637 ESTERS AND COMPOSITIONS CONTAINING SAME John J. Barch, Crestwood, -N.Y., and William M. Kraft, Verona, N.J., assignors to Tenneco Chemicals, Inc. No Drawing. Filed July 24, 1964, Ser. No. 385,045 6 Claims. (Cl. 252--56) This invention relates to a novel combination of esters and to lubricant compositions containing such esters.

With the development of jet aircraft engines that operate at extremely high altitudes and at high speeds there has been a need for lubricants having a combination of properties not possessed by conventional lubricants including mineral lubricating oils. To be useful in jet aircraft engines, the lubricant must provide good lubricity and must meet a number of rigid requirements including low pour point, high flash point, and viscosity requirements. In the past, esters prepared from a-variety of alcohols and acids have been suggested as lubricants; however, most of these esters do not have the properties required for jet engines. Esters of neopentyl alcohols and monobasic acids or monobasic and dibasic acids have been suggested which meet the requirements of the less stringent specifications, for example, Military Specification MIL-L-7808, but do not meet the requirements of the more stringent Military Specification MIL-L-23699.

A combination of two esters has been discovered that meets the requirements of base fluids for MILL-23699 lubricants. The combinations of esters contains from 67 to 73 parts of trimethylolpropane tripelargonate and from 33 to 27 parts of pentaerythritol dipelargonate di-2- methylpentanoate in each 100 parts by weight of these two esters. This combination of esters meets the requirements including the low temperature stability requirements, although neither one of these esters alone meets the low temperature stability requirements.

The esters may be readily produced in a conventional manner. The trirnethylolpropane ester can be produced by reacting three moles of pelargonic acid with one mole of the alcohol, C H C(CH OH) The pentaerythritol ester can be produced by reacting one mole of this alcohol, either sequentially or simultaneously, with two moles of pelargonic acid and two moles of Z-methylpentanoic acid. Equivalent amounts of alcohol and acid or an excess of either may be used in the reaction. The reaction may be effected in the absence or presence of an esterification catalyst, for example, p-toluenesulfonic acid. The product of the esterification may be purified by conventional procedures. For example, unreacted acid may be removed by washing witha dilute alkaline solution, valatile impurities by distillation, and certain other impurities by treatment with activated carbon.

The combination of trimethylolpropane and pentaerythritol esters may be used directly as lubricants or the esters may be blended with other base fluids to obtain lubricants containing a major amount of the esters and having special characteristics. It also may be desirable to add to the esters minor amounts of certain of the well known lubricant additives such as viscosity index improvers, pour point depressors, detergents, and corrosion inhibitors. In general it is desirable to add antioxidants, for example, phenyl a naphthylamine, 2,2-dipyridylamine, phenothiazine, or mixtures thereof. A preferred antioxidant is a mixture of phenyl-a-naphthylamine and a metal chelate which may be prepared from salicyladehyde or S-nitro-salicylaldehyde, an amine, and the metal as the chloride in the manner described in Shriner and Fuson, Systematic Identification of Organic Compounds, 4th edition, page 125. Representative, but not the only amines, are aniline, p-phenoxyaniline, p-phenoxyphenoxy aniline, O-tOlllidine, o-chloroaniline, and 2-ethylhexylamine. The metal may be nickel, cobalt, or zinc. Mix- 3,223,637 Patented Dec. 14, 1965 tures of the chelates may be used or mixtures of the chelates and other antioxidants may be used. A preferred antioxidant is a mixture of phenyl-a-naphthylamine and a nickel chelate. The aforementioned chelates may be represented by the formula:

wherein Y represents N0 or H; M represents Ni, Co, or Zn; R represents and X represents H, CH or Cl.

In the following examples all percentages and parts are by weight. The tests on the various compositions were madeinaccordance with the Military Specification MIL L23699 (WEP), June 6, 1963, Lubricating Oil, Aircraft Turboprop and Turboshaft Engines, Synthetic Base. All viscosities are expressed in centistokes.

EXAMPLE 1 A lubricant composition was prepared by mixing the following materials: parts trimethylolpropane tripelargonate 30 parts pent-aerythritol dipelargonate di-Z-methylpentanoate 2 parts phenyl-u-naphthylamine 0.2 part nickel bis(N-phenyl-S-nitrosalicylirnine) A portion was cooled to 40 F. and the viscosity determined, ASTM D445, with the following results:

Cs. Initial 7,298 After 3 hours 7,298 After 7 hours 8,042

There Was no crystallization upon standing at this low temperature.

EXAMPLE 2 Trimethylolpropane tripelargonate alone and combinations of this ester and antioxidants were tested for crystallization upon standing at 40 F. The amounts of antidoxidant and ester set forth in the following table are parts by weight:

Crystals appeared in each of the compositions after being held for about three hours at -40 F.

3 EXAMPLE 3 Base fluids of pentaerythritol dipelargonate di-Z-methyl pentanoate alone and this ester with antioxidant were cooled to --40 F. and were found to crystallize and not None :of the above fluids were stable .for 72 hours at 40 F. Crystals formed in Composition H after three hours and Composition G after .24 hours. Compositions E and .F did not develop crystals until after 40 hours and meet the specification for stability at this temperature. 5 48 hours, respectively.

The base fluid containing antioxidant contained 2% phenyl-a-naphthylamine, 0.3% nickel bis(N-phenyl-5- EXAMPLE 5 ggg' ylmme) and 0 mckel bls N phenyl sahcy A lubricant composition was prepared by mixing the EXAMPLE 4 following ingredients.

Base fluids were prepared containing both trimethyl-ol- Base fluid! Parts propane tripelargonate and penaterythritol dipelargonate Mixed esters 99 di-Z-methypentanoate in addition to antioxidants. Th se Pol ester 1 y fluids were tested for stability against crystallation at 1 -40 -F. None of the fluids were stable: for 72 hours as Total 0 required.

The compositions, parts by weight, were as follows: Antloxldant' T bl l Phenyl-a-naphthylamine 2 a e I Nickel bis(N-phenyl-S-nitrosalicylimine) 0.2

Compositions Total E F G H NOTE.T11e mixed esters consisted of 70% trimethylol tripelargonate and pentaerythritol dipelargonate di-2- methylpentanoate. The polyester was prepared by reacting Trimethylolpropane tripelargonateuun 75 65 60 55 25 under esterification conditions one mole of pentaerythritol, Pentaerythritol dipelargonate di-2- 0.75 mole of succinic anhydride, and 2.5 moles of pelargonlc methylpentanoate 25 4O acid. Phenyl-q-naphthylamine 2 2 2 2 Nlckel ms N'pheny15'mtrSahcyhmme The foregoing lubricant was subjected to various tests Total 102.2 102.2 1022 0 -2 30 with the results being set forth in the following table:

T able III Specification Require- Test Results mcnts MIL-L-23699 Viscosity, cs. (ASIM D445):

At 210 F 5.0 min-5.5 max.

At 100 F mm. At 40 F 13,000 max Stability at -40 F.:

After 3 hours, percent viscosity change- 0 6 max. After 72 hours, cs 8,032 17,000 max Flash point (ASTM D92) 425 F. min Pour Point (ASTM D97) 75 F F. max Total Acid No. 0.24. 0.5 max. Evaporation Loss (ASTM D972), 6.5 3.1% 20% max.

Hours, 400 F., atmospheric pressure. Lead Corrosion (SOD), mg./sq. in. loss, 1 4.8 mg 6 mg. max. hour at 325 F.

Foaming, M1. foam after 5-minute blow period-settling period to zero volume 20 ml.-10 sec 25 ml.60 sec. max. 10 ml.15 see. 25 ml.60 sec. max. Seq. III 20 nil.l0 sec. 25 ml.-60 see. max. Rubber (H) swell, percent change 11.43 15% min.-35% max. Thermal Stability:

Viscggiy change, percent of original at +08% i5%.

10 Total Acid No. change 1.9 2 max. Appearance Dark, no precipitate. N0 insolubles, phase Storage Stability at 230 F.:

48 Hour lead loss, mg./sq. in 168 Hour lead loss, mg./sq. in Sill??? gtability, percent Viscosity loss at Corrosion and Oxidation Stability:

After 72 Hours at 100 F.:

Percent Viscosity change at 100 F.

old No. change 0 07 Metal Wt. Change, mg./sq. in.:

Total A Aluminum "Ma nesium Copper Ryder Gear Test Average 4 Determinations, percent Reference Oil B.

separation or sediment.

25 max. max. 4 max.

The lubricating oil met all of the above-mentioned major requirements and met all of the minor requirements except for the minimum rubber swelling requirement which is a relatively minor requirement and not one to rule out use of the lubricant.

The small amount of polyester was included to effect a slight increase in the viscosity at 210 F. as the base fluid without the polyester was borderline as to meeting this test. Small amounts of other relatively more viscous esters, usually constituting less than of mixed esters of the present invention, may be used for the same purpose.

What is claimed is:

1. A composition comprising from 67 to 73 parts of trimethylolpropane tripelargonate and from 33 to 27 parts of pentaerythritol di-pelargonate di-Z-methylpentanoate per each 100 parts total weight of trimethylolpropane tripelargonate and pentaerythritol dipelargonate di-Z-methylpentanoate.

2. A composition comprising 70 parts by weight of trimethylolpropane tripelargonate and 30 parts by Weight of pentaerythritol dipelargonate di-2-methylpentanoate.

3. A lubricant composition comprising a base fluid, at least 50% of the base fluid consisting of the combination of from 67 to 73 parts by weight of trimethylolpr-opane tripelargonate and from 33 to 27 parts by weight of pentaerythritol dipelargonate di-2-methylpentanoate.

4. A lubricant composition comprising base fluid and antioxidant for the base fluid, at least 90% of the base fluid consisting of the combination of from 67 to 73 parts .by weight of trimethylolpropane tripelargonate and from 33 to 27 parts by weight of pentaerythritol dipelargonate di-2-methylpentanoate.

and 30% by weight of pentaerythritol dipelargonate di-2- methylpentanoate.

References Cited by the Examiner UNITED STATES PATENTS 2,615,860 10/1952 Burgess 260429 2,991,297 7/1961 Cooley et a1 25256 X 3,000,827 9/1961 M'oler 252-56 3,000,917 9/1961 Babayan. 3,036,005 5/1962 Koch 252-49.6 3,065,180 11/1962 Pethri-ck et a1 25256 OTHER REFERENCES Calvin et al.: The 'Oxygen-Carring Synthetic Chelate Compounds, Journal of the American Chemical Society, vol. 68 (1946), pp. 2267*2273.

Marvel et al.: Heat Stability Studies on Chelates From Schiff Bases of Salicyl'aldehyde Derivates, Journal of the American Chemical, vol. (1958), pp. 8 32835.

DANIEL E. WYMAN, Primary Examiner. 

3. A LUBRICANT COMPOSITION COMPRISING A BASE FLUID, AT LEAST 50% OF THE BASE FLUID CONSISTING OF THE COMBINATION OF FROM 67 TO 73 PARTS BY WEIGHT OF TRIMETHYLOLPROPANE TRIPELARGONATE AND FROM 33 TO 27 PARTS BY WEIGHT OF PENTAERYTHRITOL DIPELARGONATE DI-2-METHYLPENTANOATE. 